Usually such is a hardware problem...
Have you checked cooling?
Will it shut off if you use only 1 thread and keep load average low?_________________Intel Core i7 2700K@ 4.1GHz/HD3000 graphics/8GB DDR3/180GB SSDWhat am I supposed to be advocating?

Yes great it works if I am using only one thread then it is able to process 22 packages without doing automaticly power off, it is slow I only can see -> us 25%, sys 0%, id 75%, wa 0% but .......it is stable.

It is an Quad Core Machine and i am using now only one thread, but portage (emerge) sems to be happy with this situation.

There's likely a problem with overheating then. Unfortunately I don't know anything about ppc/mac hardware... You could see if it will do with 2 threads or try to limit the load average lower...

Check the heatsink for dust or a bad fan. I don't know what apple did with their os to throttle, I would hope Linux would be able to do the same, but I'm an x86/pc hardware person..._________________Intel Core i7 2700K@ 4.1GHz/HD3000 graphics/8GB DDR3/180GB SSDWhat am I supposed to be advocating?

>There's likely a problem with overheating then.
>Unfortunately I don't know anything about ppc/mac hardware...
>You could see if it will do with 2 threads or try to limit the load average lower...
The PowerMac G5 Quad Core has an Liquid Cooling System (LCS), i did install the stress application
to geto 100% CPU load constantly for 2 Minutes on all 4 CPU Cores during that stress activity i did monitor the
temperature of all the CPU Cores. CPU Core0+1 did have an average about 80 Grad Celsius, CPU Core2+3 gets to 70 Grad Celsius. I did not have any reboot during that testphase I did run the stress test several time no problem occured.
For me it looks like the portage command did have an problem with the "-j5" parameter but unfourtantly i can not reproduce the problem bcause ther are not so much packages to install wtih the emerge because the system is already updated.

>Check the heatsink for dust or a bad fan.
>I don't know what apple did with their os to throttle,
>I would hope Linux would be able to do the same, but I'm an x86/pc hardware person...
I did check in the CPU aerea and the LCS System for leakage and did remove the dust it did look clean, i did also reconnect all the connectors for the System Board and the LCS.

>Also there's the possibility that 2 minutes may not be long enough to trigger the issue...
I did increase it to 4 minutes it is still working perfect. I did repeat the test several times.....

>You can always re-emerge a package again by not specifying --update (-u). Or you could try building a new package >you never ran before I did an re-emerge an long time CPU job (emerge sys-devel/gcc) after chanceing the /etc/portage/make.conf to (MAKEOPTS="-j5 -l4.6"), running about estimatet 40 minutes with very high CPU load and more the 80 degrees Celsius without any incident. For me it looks like the problem gets fixed with the reconnecting of the connectors on the System Board and on the pump (Liquid Cooling System (LCS)).